In tall structures, such as buildings with high ceilings, the cost of the substantial structural members necessitated by the usual rigid structural designs is excessive. Shell roof constructions have been provided in an effort to reduce costs, but such structures have been rigid as, for example, that shown in U.S. Pat. No. 3,226,892.
Similarly, in structures spanning spaces such as bridges, a rigid structural design is employed (except in design of suspension bridges).
Rigid structures are designed according to classical structural analysis which assumes linear, elastic, small displacement behavior in formulating mathematical equations to determine stresses and displacements. Such structures are often prefabricated or at least partially so for erection at the job site. The prior art structures depend upon such relative rigidity retaining a static condition while resisting loads imposed thereon. Since the prior art systems resist force in bending, they must be designed of substantial members capable of resisting relatively large bending moments.